Engine starter drive



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Jam 24, J. J. DIGBY 2,495,653

ENGINE STARTER DRIVE Filed May 24, 1948 a mi z@ fr M645 l www E t I :I 2,341

WITNESS I TTRNE'Y atente Jan. 24, 1950 f Nl .STAT ES T I3GEEF-1F51CE.

ENGINE STARTE'RDRIVE v.htmesJ. Digby, Elmira, N. .zY.,f:.assignortocBen .clixAviationv Corporation, ElmiralHeig-hts; N. TY., t acorporationof Delaware 'ApplicatioMayZQ 1948,-SeriallNof28if909 'Thelfpresent invention `relates *to ,an engine starter drive and more .particularly tto ..an;.anti

masslandinertia' oftheparts are very important A inialecting thermeshing-fpperation, and in particulartheshock `loads .to whichlthe parts are subjected. .The .provisions for 'permitting slip* ping oryieldinginzcaseioftooth abutment and/or voverloading of the `:drive i should, ntherefore, .be

located-.asV closely-:as possiblezto-'the drivezpinion in.'orderltoreduce the inertia of the parts between thezpoint of .application of the loadttor'thedrive, and the pointof yieldifor relieving.: such load.

.It is an object of the present invention-.topr

vide an engine starter drive having novel :cushinning and load-,limiting means. located -close to the'drive pinion.

.It'zis f another object to provide s-uchz-a .device includingia den-talfclutch which :isiarranged to vslip on overload and whiclrs yieldingly compressedxbynan'elasticfmember inthefform of a block of elastically deformable material which is Subjectedfto:compressiononly.

.It is another objeotto"provide.suchteJ device incorporatingi a :dental overrunning Nclutch. between the slip clutch. and `the starter drive pin ion.

It yis another: object to --provide such -a: 4device 4incorporating a splinedconnection `between"the overrunning clutch r.and the pinion, and a. mesh enforcing .spring normally .holding the) pinion in fully extendedposition.

Itisf a furtherobjecttoprovide such fa device embodying ia` drive connection-irom the starting motor to .the engine gear' which.` isfpositive .and withoutI slippage untll-.a.predetermined maximum torque is exceededafter which, .slippage is aln lowed to take place yWhiletransmittingsaid maximumtorque.

Further objects and. .advantages-will:beapparentirom 'the following description taken` .in connection with the accompanying ...drawing in which:

Fig...1.isjasideielevation parth1 brokeniaway f and .in .section oa. starter drive.. forming.- aV preferredY embodiment of .therV .invention ...and

. Figlie Aa similarviewshowingthe parts-inthe positions assumed JWhile -vthe engine .is -.-being crarllced v .l LnxEgil `of the :drawing there is. illustratedxa powerfshaft I which commonly .the .-.extended armatureishaft ofxaistarting. motor not illustrated. Auscrewishaftrlsfixed on the power shaft` by suitable: meanssuchas across; pin 3,i-and a pinion is slidably journalled (on.y the power shaft. for longitudinal movementfintoand'out of mesh with airengineA gear 5.

`Means for actuating the pinion from .the screw shaft is provided `comprising a f control nut 6 threaded onthe .-screw shat,-and a driving slip or overload clutch member l fsplined on ,thernut 6 as indicated -at Briand :hav-ing inclined .teeth 9 adapted to cooperate. with simi-lar teeth I I formed onandm'ven slip clutch member I2 which .is-slidablyjournalledfonthe power `shaft I. :A :cylinclricalr4 block Y'I 3` of.elasticall57 deformable material sucheasil rubber A`.is mounted onf the 'control nut 6 between aradial flange hi thereof .and the drivingislipfclutch memberi'l.

A sleeve I-51is arranged .to .surround the control'nut,v rubberblockz I3, .and slipclutch mem bers I and 4:2, .Tandis provided with terminal flangeswl :and I'LbeariI-ig-:on` the exterior of the ange .It of-thecontrol nutand a fla-nge I8 `of thedr-iven. slip. clutch member I2. '.Sleeve 'I5 holds said. memberaunderonIy enough initial compression .to hold the overloadclutoh engageduntilthe control nut can .further compress the rubber after vthe!v .piniomengages withthe. ringgear. and torque. transmission. begins to. take. place. -Thrust rings I.9..and.2 I arepreferably, interposed between .the :.ange Il oi.sle.eve I.5.and thelange I3 of. the driven fslip..,clutch.member l2, Ain order to form athrustbearingat that.point.

.rAnove1running-. clutch. .connection between. the .drivenslip clutchwmenber `l2 v.and .thegpinion 'Il is ,provided Ncomprising Aa `driven .overrunning clutch.memb.er 2.2` splned .0n .thehub 23 .of .the pinion `.4as,in"dicatefd.at 24, andphaving clutch teeth. 25 ada ipte`ci.,.to .cooperate with similar; clutch teelth 2 I Tformed on the driven` slip clutch-member I2. `.The .overr-Imning A,clutch .teeth 25, 26. are normally lheldin .engagement lby a .spring ".21 locatedobetWeen-.a flange .23 .on the .driven overrunning clntchmemben22, .and .a thrust ring .29 xe'dly mount-.edi in .-)a barrel .member 3| which surrounds and .enclosesithe drive.

.Barrels I has rva; reducedportion 32-forming a shoulder 33 f :adapted =to ...bear against .the ango lI6 offsleevei Ir5,.\anda latchffringfis journalled on the :reduced Yportion against: said fshoulder, hengf-.retained-fthereonlzby asrlocksringrB. .The latch ring 34.1 provi-dedfwithfpockets'36adapted toccooperate :with :a `latjeh plunger -31 .-fwhichis preferably actuated by the starting switch, not illustrated, in the manner disclosed in the patent to Oliver, No. 2,444,109, issued June 29, 1948.

The barrel 3| terminates in a flange 38 arranged to cooperate with the end of the screw shaft 2 to provide an abutment for limiting the longitudinal travel of the movable parts of the drive toward meshing position. An anti-drift spring 39 is arranged to normally maintain the barrel 3| in idle position.

A compression spring 4| is mounted on the hub of the pinion 4 and bears at its ends against the driven overrunning clutch member 22 and a thrust ring 42 seated against a shoulder 43 of the pinion so as to normally maintain the pinion in extended position as deiined by a thrust ring 44 seated in a groove in the end ofthe pinion hub. A sleeve 45 is arranged to surround and enclose the spring 4| to exclude dust from the splined connection and to retain lubricant therein. The sleeve 45 is provided with a flange 45 clamped to the end of the barrel 3| against the thrust ring 2S and with an inturned ange 4l' surrounding the thrust ring 42 on the pinion. A lubricant channel 48 is preferably provided through the hub of the pinion so as to permit the space within the sleeve 45 to be used as a lubricant reservoir.

In the operation of the drive, starting with the parts in positions illustrated in Fig. 1, rotation of the power shaft in the direction of the arrow (a) causes the control nut and its associated parts to be traversed to the right until the pinion 4 is meshed with the ring gear 5 of the engine and its further motion is arrested by the abutment of the flange 38 of the barrel against the end of the screw shaft 2. Torque is then transmitted through the overload slip clutch I2 and the over-running clutch l2, 22 to the pinion to rotate the engine gear. This torque causes a longitudinal thrust to be developed by the screwjack action of the nut and screw shaft, which tends to compress further the rubber block I3, such compression being permitted by the splined connection B between the driving overload clutch member l and the nut 5. The longitudinal movement of the nut 6 to so compress the rubber block I3 is limited by its abutment against a thrust bearing provided by the driven overload clutch member I2. In order to regulate the compression of the rubber block, one or more thrust washers 49 are interposed between the end of the control nut and the driven overload clutch member I2.

The slope of the teeth 9, II on the overload clutch members 'I and I2 is made approximately equal to the helix angle of the triple threads so that the clutch will not open before the control nut moves forward to its terminal position against the thrust Washers at the end of the control nut. It is important to keep the initial compression of the rubber as low as possible in order to assist the mesh-enforcing spring 4| to provide a soft endwise cushion when the pinion strikes the ring gear. The amount of torque that the drive overload clutch will transmit is regulated by the travel of the control nut in further compressing the rubber. The travel is adjusted by adding or removing thrust washers 49 at the end of the control nut. If the predetermined maximum torque is exceeded momentarily by shock loads applied to the drive during the meshing operation or at any other time, the longitudinal thrust of the slip clutch teeth becomes large enough to still further compress the rubber block I3 sufciently to allow the clutch teeth to ratchet over each other, thus slipping oi the excessive torque loads.

When the engine fires, the acceleration of the pinion 4 causes it to overrun the drive, this being permitted by the overrunning clutch connection I2, 22. As long as the starting switch is held closed, the plunger 31 enters and remains in a pocket 36 of the latch ring 34 as shown in Fig. 2, whereby demeshing of the pinion 4 from the ring gear 5 is prevented. When the starting switch is opened, the plunger 31 is withdrawn so as to permit the parts to be returned to their idle positions by the acceleration transmitted from the engine gear through the pinion.

If during the meshing operation a tooth of the pinion should abut against a tooth of the ring gear 5, the splined connection between the pinion and the driven overrunning clutch member 22 permits the longitudinal travel of the control nut and its associated parts to continue after the movement of the pinion is thus arrested so as to build up suiiicient torque to index the teeth of the pinion into proper registry with the tooth spaces of the ring gear, while compressing the mesh-enforcing spring 4 I. When such registry is secured, the spring 4| snaps the pinion into mesh So as to avoid the possibility of milling action of the pinion teeth on the ring gear.

It will be noted that the yielding mesh-enforcing connection for the pinion, and the yielding slip connection for relieving excess torque loads are both located as close as possible to the pinion. The inertia of the parts involved in the yielding and mesh-enforcing functions is consequently very small so that these functions are performed quickly and with a minimum of shock. Without the spring 4| the heavy drive would quickly damage the ring gear teeth but with the'spring, ring gear life is better than would be the case with a lighter meshing mass without a mesh-enforcing spring. The heavy meshing mass of this drive is an advantage in that it improves cold weather meshing.

Although but one embodiment of the invention has been shown and described in detail, it will be understood that other embodiments are possible and that various changes may be made in the design and arrangement of the parts Without departing from the spirit of the invention.

I claim:

l. In an engine starter drive a power shaft, a screw shaft fixed thereon, a pinion journalled on the power shaft for longitudinal movement into and out of mesh with a gear of an engine to be started, a nut on the screw shaft, a driving slip clutch member having inclined torque-transmitting teeth splined on the nut, a driven slip clutch member having cooperating inclined teeth journalled on the power shaft, an elastic com pression member on the nut engaging the driving clutch member, a sleeve engaging at its ends the nut and driven clutch member and holding the clutch members and elastic member under compression, means connecting the driven clutch member to the pinion including a transmission member splined on the pinion, yielding mesh enforcing means urging the pinion into extended relation with respect to the transmission member, and means for retaining the transmission member on the pinion. 'Y

2. An engine starter drive as set forth in claim 1 in which the driven slip clutch member and the transmission member are provided with cooperating overrunning clutch teeth, and including further yielding means for causing engagement of said overrunning clutch teeth.

3. An engine starter drive as set forth in claim- 1 49ans 5 including further telescopic means for enolpsin the splined connection and mesh-enforcing means.

4. An engine starter drive as set forth in claim 2 including further a barrel member enclosing.` the driving connection from the screw shaftgtothe pinion and having means for maintainingl the yielding overrunning clutch means under compression and for limiting the meshing movement of the pinion.

5. An engine starter drive as set forth in claim 2 including further a barrel member enclosing the driving connection from the screw shaft to the pinion and having abutments for maintaining the yielding overrunning clutch means under compression and for limiting the longitudinal travel of the clutch memberstoward the engine m'ember, the pitch of the threads of the screw shaft being substantially the same as the slope of the teeth of the slip clutch.

JAMES J. DIGBY.

No references cited. 

